According to the related art, two optical waveguides are used to bi-directionally transmit an optical signal, so that the two optical waveguides are classified into a transmitting optical waveguide and a receiving optical waveguide to transmit the bi-directional optical signals. However, according to the related art, since two optical waveguides are used over the whole optical signal transmission path, the whole optical signal transmission path may be huge.
In addition, differently from the scheme of bi-directional transmission of optical signals described above, as another example of the relate art, there is a scheme of transmitting and receiving optical signals through a single optical waveguide by using the difference in wavelength or polarization. However, since the scheme is required to provide a separated optical device having a function of separating an optical signal on a waveguide according to the wavelength or polarization, the scheme may be complexed in structure.
Thus, in the present disclosure, there is proposed a waveguide having a bi-directional optical transmission structure, which refracts or reflects transmitting and receiving optical signal incident upon a reflector in mutually different forms by using the reflector arranged at an intersection where a main waveguide crosses a branch waveguide connected to at least one of the opposite ends of the main waveguide, instead of the separated optical device.